The present invention pertains to a receptacle arrangement for a cable end piece having a sheath that is at least partially removed at the end, exposing at least one signal conductor, especially an optical fiber, and the end of an elongated stress-relief device. The present invention also pertains to a receptacle arrangement having a container with an inlet orifice into which the cable end piece is inserted, and with an outlet orifice through which at least the signal conductors exit, and a casting compound surrounding the signal conductors, the ends of the stress-relief device and the cable sheath in the container.
Methods of protecting cable connections against external influences are described in U.S. Pat. No. 4,319,802 and U.S. Pat. No. 4,447,120. In these patents, the sheath is removed from the cable end pieces and the end of a stress-relief device in the cable is secured by crimping (e.g., on a metal sleeve). The signal conductor, especially an optical fiber that is sensitive to kinks, is also exposed to external shearing effects. Crimping cannot assure a homogeneous transmission of forces. Instead, a few fibers carry a disproportionate amount of the forces, especially with a fiber-shaped stress-relief device. The cable sheath must be secured separately against twisting due to torsion.
U.S. Pat. No. 4,984,865 discloses a receptacle arrangement for a cable end piece where the cable sheath is partially removed at the end, thus exposing the end of an optical fiber and the end of an elongated stress-relief device. The end piece is inserted into a plug connector housing that contains a thermoplastic material. This known receptacle arrangement does not assure that the cable sheath will be reliably secured at high tensile forces or that there will be a symmetrical distribution of fibers. There is a danger that the fibers might collapse during injection or fusion of the thermoplastic material, which is introduced in the form of granules.
German patent (OLS) 3,820,950 describes a receptacle arrangement of the type described above, but with an improvement with regard to the problem of securing the stress-relief device symmetrically. The cable end piece from which some of the cable sheath is removed at the end is inserted through an inlet orifice into a container. Removing some of the cable sheath at the end exposes an optical fiber and the end of an elongated stress-relief device (Aramid fibers). The optical fiber exist through an outlet orifice of the container. After inserting the cable end piece, a material that can be injected and hardened is introduced into the container in liquid or molten form in front of the exposed ends of the fibers. This known receptacle arrangement is relatively expensive to manufacture because it requires an injection molding machine. The material that is injected at about 200.degree. C. represents a great thermal stress for the optical fiber which is very sensitive to temperature. The shield-like fanning out of the ends of the stress-relief device, which is to be achieved with the injection, is not always assured in practice. If the distribution of force at the ends of the stress-relief device is not homogeneous, this may result in breakage of individual stress-relief fibers.
With the known type of receptacle, the cable sheath is not secured to prevent it from twisting with respect to the container. When tensile forces act on the sheath, there is a substantial risk that the sheath can be pulled relatively easily out of the casting compound. German patent (OLS) 3,820,950 does not describe any anti-kink protection (maintaining a minimum bending radius) for the cable end piece.
Therefore, an object of the present invention is to create a receptacle arrangement that provides the most comprehensive possible protection for the cable end piece and the signal conductor from external stresses, especially tensile, shearing and torsional stresses.